Laminated film and method for manufacturing laminated film

Abstract

[Problem] To provide a laminated film that can provide a resin sheet having both high smoothness and good lubricity. [Solution] This laminated film has a polyester base material film, a release layer, and a resin sheet disposed on the opposite surface of the release layer to the base material. The resin sheet is obtained by curing a resin sheet-forming composition containing a resin component (A) and a crosslinking agent (B). The resin sheet contains substantially no particles. The film thickness (t1) of the resin sheet is 1-20 μm. The arithmetic average height (Sa) of a surface (1) of the resin sheet is 2-30 nm. The indentation modulus of elasticity (E1) of a surface (1) of the resin sheet is at least 2.0 MPa. The indentation modulus of elasticity (E2) of a surface (2) of the resin sheet is at least 2.0 MPa. The absolute value of the difference between E1 and E2 is at most 1.5. The coefficient of static friction, as measured when the surface (1) of the resin sheet (1) on the opposite side to the release layer surface is overlaid on the surface (2) of the resin sheet on the side of the release layer, is at most 1.5.

Description

[Technical Field]

[0001] This invention relates to a laminated film made by laminating resin sheets, and more particularly to a laminated film made by laminating resin sheets used in electronic components and optical applications. [Background technology]

[0002] Conventionally, release films based on polyester film have been used as process films in solution-based film formation of resin sheets such as adhesive sheets, cover films, polymer electrolyte membranes, and dielectric resin sheets, due to their high heat resistance and mechanical properties. In recent years, high smoothness and transparency are required for resin sheets used in electronic components such as dielectric resin sheets used in film capacitors and for optical applications, and therefore, high smoothness has been required for the surface of release films used as process films. For this reason, technologies such as those described in Patent Documents 1 to 3 have been disclosed, and films with reduced surface roughness on the surface of the release layer have been proposed.

[0003] However, in optical applications, for example, high smoothness is required to improve transparency, but if the smoothness is too high, the slipperiness deteriorates, and there is a risk of scratches occurring during the transport process, leading to a decrease in yield. Also, in electronic component applications such as film capacitors, smoothness is required to improve electrical properties such as dielectric breakdown voltage, but if the smoothness is too high, the slipperiness deteriorates, and there is a concern that winding misalignment and wrinkles may occur when winding the dielectric resin sheet onto a roll, making it difficult to wind properly and reducing the performance of the film capacitor.

[0004] To improve these issues, Patent Document 4 proposes adding specific particles to resin sheets used for optical purposes, such as polarizers, to give them slipperiness. Furthermore, Patent Document 5 proposes a method for transferring particles from a base film to a resin sheet used for films in film capacitors and the like. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-144021 [Patent Document 2] Japanese Patent Publication No. 2014-154273 [Patent Document 3] Japanese Patent Publication No. 2015-182261 [Patent Document 4] Japanese Patent Publication No. 2019-95661 [Patent Document 5] International Publication No. 2020 / 039638 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the method described in Patent Document 4 involves incorporating particles into the resin sheet, raising concerns about insufficient transparency due to increased internal haze. Furthermore, the method described in Patent Document 5 may result in uneven transfer of particles to the resin sheet, raising concerns about unstable slipperiness. The present invention solves the above problems and proposes a laminated film that can provide a resin sheet that is highly smooth and has good slipperiness without substantially adding particles inside the resin sheet. [Means for solving the problem]

[0007] As a result of diligent research, the inventors discovered that by applying a coating solution containing at least a specific resin and a crosslinking agent to a smooth substrate film under specific conditions, and then drying and curing it, they were able to form irregularities on the surface of the laminated film caused by a phase separation structure, and succeeded in providing good slipperiness without including particles.

[0008] The inventors have further discovered that by coating, drying, and curing under specific conditions, the resin and crosslinking agent in the resin sheet can be made uniform, thereby reducing the difference in physical properties between the front and back surfaces of the resin sheet.

[0009] In other words, the present invention consists of the following configuration. [1] A polyester-based base film, a release layer disposed on at least one side of the base film, and a resin sheet disposed on the side of the release layer opposite to the base film, Laminated films that satisfy the following (1) to (7): (1) The resin sheet is formed by a resin sheet containing at least a resin component (A) and a crosslinking agent (B). The composition has been cured. (2) The resin sheet contains substantially no particles, (3) The film thickness (t1) of the resin sheet is 1 μm or more and 20 μm or less. (4) The indentation modulus (E1) of the resin sheet surface (1) is 2.0 MPa or higher. (5) The indentation modulus (E2) of the resin sheet surface (2) is 2.0 MPa or higher. (6) The absolute value of the difference between E1 and E2 is 1.5 or less. (7) The static friction coefficient measured by overlapping the surface (1) of the resin sheet opposite to the release layer surface and the surface (2) of the resin sheet on the release layer side is 1.5 or less. [2] In one embodiment, the arithmetic mean height (Sa) of the surface (1) of the resin sheet is 2 nm or more and 30 nm or less. [3] In one embodiment, the maximum cross-sectional height (St) of the surface (1) of the resin sheet is 80 nm or more and 1000 nm or less. [4] In one embodiment, the crosslinking agent (B) contained in the resin sheet forming composition is liquid at 30°C. [5] In one embodiment, the proportion of the crosslinking agent (B) contained in the resin sheet to the total resin sheet is 10% by mass or more. [6] In one embodiment, the weight-average molecular weight of the resin component (A) contained in the resin sheet is 10,000 or more. [7] In one embodiment, the surface free energy of the release layer surface is 40 mJ / m 2 The following conditions apply, and the adhesion energy is 3.5 mJ / m 2 That's all. [8] In one embodiment, the arithmetic mean height (Sa) of the release layer side surface of the base film is 20 nm or less, and the maximum protrusion height (P) is 500 nm or less. [9] In another aspect, the present invention provides a method for producing a laminated film according to any one of the above, wherein the method is characterized by applying and forming a resin sheet on a base film by a solution casting method.

[10] In one aspect, the present invention provides a resin sheet satisfying the following. (1) The resin sheet is obtained by curing a resin sheet-forming composition containing at least a resin component (A) and a crosslinking agent (B), (2) The resin sheet contains substantially no particles, (3) The film thickness (t1) of the resin sheet is 1 µm or more and 20 µm or less, (4) The indentation elastic modulus (E1) of the resin sheet surface (1) is 2.0 MPa or more, (5) The indentation elastic modulus (E2) of the resin sheet surface (2) is 2.0 MPa or more, (6) The absolute value of the difference between E1 and E2 is 1.5 or less, (7) The static friction coefficient measured by overlapping one surface (1) of the resin sheet and the opposite surface (2) of the resin sheet opposite to said surface (1) is 1.5 or less.

[11] In another aspect, the present invention provides a resin sheet which is a sheet peeled from a release film having a base material and a release layer, wherein the release layer has a surface free energy of 40 mJ / m 2 or less, and an adhesion energy of 3.5 mJ / m 2 or more. Here, the resin sheet of the present invention is preferably a sheet peeled from a release film having a predetermined surface free energy. However, it is not easy to identify the structure of the resin sheet obtained by peeling from the release film and to define the claims based thereon, and there are impractical circumstances. For this reason, the release film of the present invention is defined in the form of a product-by-process claim. Advantageous Effects of the Invention

[0010] By using the laminated film of the present invention, it is possible to provide a resin sheet that is highly smooth, has good slipperiness, and has uniform physical properties. By using the resin sheet molded according to the present invention, it is possible to provide good products for various applications. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing the structure of the present invention. [Figure 2] This is a schematic cross-sectional view illustrating the configuration of the present invention in one embodiment. [Modes for carrying out the invention]

[0012] As shown in Figure 1, the laminated film of the present invention is a laminated film having a polyester-based base film 10, a release layer 11 disposed on at least one side of the base film 10, and a resin sheet 12 disposed on the side of the release layer 11 opposite to the base film 10.

[0013] The present invention provides a resin sheet that, for example in optical applications, can enhance transparency and other properties, and moreover, can provide a resin sheet that exhibits high smoothness. Furthermore, it can provide a resin sheet that was previously difficult to achieve. It achieves both high smoothness and high slipperiness, which, for example, can suppress scratches during the conveying process and avoid a decrease in yield. Furthermore, for example, in electronic component applications such as film capacitors, it is possible to provide resin sheets that exhibit high smoothness, and the resin sheets can improve electrical properties such as dielectric breakdown voltage. Moreover, it is possible to achieve both high smoothness and high slipperiness, which was previously difficult, and for example, when winding dielectric resin sheets onto a roll, winding misalignment and wrinkle inclusion can be suppressed. It exhibits excellent winding properties. Therefore, it can be transported while maintaining superior capacitor performance. Furthermore, the present invention makes it possible to avoid insufficient transparency, such as increased internal haze, by making the resin sheet substantially particle-free. It also avoids the problem of uneven distribution of particles transferred to the resin sheet, resulting in good slipperiness.

[0014] (Base film) The present invention has a polyester-based base film. The polyester constituting the polyester film used as the base of the present invention is not particularly limited, and a film made from polyester commonly used as a base film can be used. Preferably, it is a crystalline linear saturated polyester consisting of an aromatic dibasic acid component and a diol component, and for example, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or copolymers mainly composed of these resin components are more preferable. In particular, a polyester film formed from polyethylene terephthalate is especially preferable. The polyethylene terephthalate preferably has a repeating unit content of ethylene terephthalate of 90 mol% or more, more preferably 95 mol% or more, and may also contain small amounts of other dicarboxylic acid components and diol components copolymerized. From a cost standpoint, it is preferable to produce a product made solely from terephthalic acid and ethylene glycol. Furthermore, known additives, such as antioxidants, light stabilizers, ultraviolet absorbers, and crystallizers, may be added within a range that does not impair the effects of the film of the present invention. The polyester film is preferably a biaxially oriented polyester film due to reasons such as its high bidirectional modulus of elasticity.

[0015] The intrinsic viscosity of the polyethylene terephthalate film described above is preferably 0.50 to 0.70 dl / g, and more preferably 0.52 to 0.62 dl / g. An intrinsic viscosity of 0.50 dl / g or higher is preferable because it prevents frequent breakage during the stretching process. Conversely, an intrinsic viscosity of 0.70 dl / g or lower is preferable because it allows for good cutability when cutting to a predetermined product width and prevents dimensional defects. Furthermore, it is preferable to thoroughly vacuum-dry the raw material pellets.

[0016] The method for manufacturing the polyester film in the present invention is not particularly limited, and conventional methods can be used. For example, the polyester can be melted in an extruder, extruded into a film, cooled in a rotating cooling drum to obtain an unstretched film, and then stretched. Biaxial stretching is preferred for its mechanical properties. A biaxially oriented film can be obtained by sequentially biaxially stretching a uniaxially oriented film in the longitudinal or transverse direction in the transverse or longitudinal direction, or by simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions.

[0017] In the present invention, it is preferable that the stretching temperature during stretching of the polyester film be above the secondary transition temperature (Tg) of the polyester. It is also preferable to stretch the film by 1 to 8 times, and particularly 2 to 6 times, in both the longitudinal and transverse directions.

[0018] The polyester film described above preferably has a thickness of 6 μm to 50 μm, more preferably 8 μm to 31 μm, and more preferably 10 μm to 28 μm. A film thickness of 6 μm or more is preferable because there is no risk of deformation due to heat during film production, release layer processing, and resin sheet molding. On the other hand, a film thickness of 50 μm or less is preferable because the winding diameter when wound into a roll is small, and the winding length of the resin sheet to be molded can be increased. When the polyester film used as the base film has a multilayer structure as described later, the overall film thickness of the base film falls within the above range.

[0019] The polyester film described above may be a single layer or a multilayer of two or more layers. It is preferable that at least one side has a surface layer A that is substantially free of particles. In one embodiment, the polyester film which is the base film has a surface layer A on the side facing the resin sheet. When the base film is a laminated polyester film consisting of two or more multilayer layers, it is preferable that the side opposite to the surface layer A, which is substantially free of particles, has a surface layer B that can contain particles. As for the laminated structure, if the layer on the side where the resin sheet is placed is the surface layer A, the layer on the opposite side is the surface layer B, and the other core layers are layers C, then the layer configuration in the thickness direction can be a laminated structure such as A / B or A / C / B. Layer C may consist of multiple layers. Furthermore, the surface layer B may not contain particles. In that case, it is preferable to provide a coating layer containing particles and a binder on the surface layer B to impart slipperiness for winding the film into a roll.

[0020] In the polyester film of the present invention, it is preferable that the surface layer A located on the surface where the resin sheet is molded does not substantially contain particles. Furthermore, it is preferable that the arithmetic mean height (Sa) of the surface layer A of the polyester film, that is, the arithmetic mean height (Sa) of the release layer side surface of the base film, is 20 nm or less. Moreover, it is particularly preferable that the arithmetic mean height (Sa) is 10 nm or less. When Sa is 20 nm or less, it is preferable that pinholes and localized thickness unevenness do not occur during the molding of the resin sheet. It can be said that the smaller the arithmetic mean height (Sa) of the surface layer A, the better, but it may be 0.1 nm or more. Here, if a release layer, etc., described later is provided on the surface layer A, it is preferable that the release layer does not substantially contain particles, and it is preferable that the arithmetic mean height (Sa) after the release layer is laminated falls within the above range. In the present invention, "substantially containing particles" means, for example, in the case of inorganic particles, that the content is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit when inorganic elements are quantified by fluorescence X-ray analysis. This is because even without actively adding particles to the film, contaminants originating from foreign substances, or dirt adhering to the raw resin or the production lines and equipment during the film manufacturing process, can detach and become mixed into the film.

[0021] The maximum protrusion height (P) of the surface layer A of the polyester film, that is, the maximum protrusion height (P) of the release layer side surface of the base film, is, for example, 500 nm or less, preferably 200 nm or less, more preferably 150 nm or less, even more preferably 100 nm or less, for example 85 nm or less, and particularly preferably 50 nm or less. If the maximum protrusion height (P) is 500 nm or less, defects such as pinholes and localized thinning do not occur during resin sheet formation, resulting in a good yield, which is preferable. The P of the surface layer A of the polyester film is preferable as it is small, but it may be 1 nm or more, or 3 nm or more. Here, if a release layer or the like described later is provided on the surface layer A, it is preferable that the maximum protrusion height (P) after the release layer is laminated falls within the above range.

[0022] In the polyester film of the present invention, the surface layer B that forms the opposite side of surface layer A preferably contains particles from the viewpoint of the film's slipperiness and ease of air release, and it is particularly preferable to use silica particles and / or calcium carbonate particles. The particle content is preferably 5,000 to 15,000 ppm in total in surface layer B. At this time, the arithmetic mean height (Sa) of the film of surface layer B is preferably in the range of 1 to 40 nm. More preferably, it is in the range of 5 to 35 nm. When the total amount of silica particles and / or calcium carbonate particles is 5,000 ppm or more and Sa is 1 nm or more, when the film is wound into a roll, air can be released uniformly, resulting in a good winding shape and good flatness, making it suitable for the manufacture of resin sheets. Furthermore, when the total amount of silica particles and / or calcium carbonate particles is 15,000 ppm or less and Sa is 40 nm or less, lubricant aggregation is less likely to occur, and no coarse protrusions are formed, resulting in stable quality during resin sheet molding, which is preferable.

[0023] The particles contained in the surface layer B described above can be inert inorganic particles and / or heat-resistant organic particles other than silica and / or calcium carbonate. From the viewpoint of transparency and cost, silica particles and / or calcium carbonate particles are more preferable, but other inorganic particles that can be used include alumina-silica composite oxide particles and hydroxyapatite particles. Heat-resistant organic particles include cross-linked polyacrylic particles, cross-linked polystyrene particles and benzoguanamine particles. When silica particles are used, porous colloidal silica is preferred, and when calcium carbonate particles are used, light calcium carbonate surface-treated with a polyacrylic acid polymer compound is preferred from the viewpoint of preventing lubricant detachment.

[0024] The average particle size of the particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, and particularly preferably 0.5 μm or more and 1.0 μm or less. An average particle size of 0.1 μm or more is preferable because it provides good slipperiness to the base film. Furthermore, an average particle size of 2.0 μm or less is preferable because it eliminates the risk of pinholes occurring in the resin sheet due to coarse particles in the surface layer B.

[0025] The surface layer B described above may contain two or more types of particles made of different materials. It may also contain particles of the same type but with different average particle sizes.

[0026] If the surface layer B does not contain particles, it is preferable to provide slipperiness by applying a coating layer containing particles on the surface layer B. This coating layer is not particularly limited, but it is preferable to provide it as an in-line coating applied during the formation of the polyester film. If the surface layer B does not contain particles, and the surface layer B has a coating layer containing particles, the surface of the coating layer preferably has an arithmetic mean height (Sa) in the range of 1 to 40 nm, for the same reasons as the arithmetic mean height (Sa) of the surface layer B described above. More preferably, it is in the range of 5 to 35 nm.

[0027] In the surface layer A, which is the layer on which the above-mentioned resin sheet is provided, it is preferable not to use recycled materials or the like in order to prevent the inclusion of particles such as lubricants, from the viewpoint of reducing pinholes.

[0028] The thickness ratio of surface layer A, which is the layer on which the above-mentioned resin sheet is provided, is preferably 20% to 50% of the total thickness of the base film. If it is 20% or more, the influence of particles contained in surface layer B and the like from inside the film is less likely to occur, and it is preferable that the arithmetic mean height (Sa) easily satisfies the above range. If it is 50% or less of the total thickness of the base film, the proportion of recycled materials used in surface layer B can be increased, which is preferable as it reduces the environmental burden.

[0029] Furthermore, from an economic standpoint, 50 to 90% by mass of recycled film scraps or PET bottles can be used in layers other than the surface layer A (surface layer B or the aforementioned intermediate layer C). Even in this case, it is preferable that the type, amount, particle size, and arithmetic mean height (Sa) of the lubricant contained in surface layer B satisfy the above range.

[0030] Furthermore, a coating layer may be applied to the surface of surface layer A and / or surface layer B before stretching or after uniaxial stretching during the film-forming process to improve the adhesion of a release layer or other layer applied later, or to prevent static electricity. Corona treatment may also be applied. When a coating layer is applied to surface layer A, it is preferable that the coating layer is substantially free of particles.

[0031] (Release layer) The present invention has a release layer disposed on at least one side of a base film, for example, a release layer between the base film and a resin sheet. The resin constituting the release layer is not particularly limited, and silicone resins, fluororesins, alkyd resins, various waxes, aliphatic olefins, etc., can be used, and each resin can be used alone or in combination of two or more types. If the resin sheet described later contains a crosslinking agent, it is preferable to include a silicone resin because it improves the release properties. In this specification, the substrate and the release layer laminate may be simply referred to as the release film.

[0032] The release layer may include, for example, a silicone resin. Silicone resins are resins that have a silicone structure in their molecules, and examples include curable silicones, silicone graft resins, and modified silicone resins such as alkyl-modified resins. However, from the viewpoint of migration properties, it is preferable to use a reactive curable silicone resin. Reactive curable silicone resins can include those that are addition reaction type, condensation reaction type, or ultraviolet or electron beam curable type. More preferably, low-temperature curable addition reaction type resins that can be processed at low temperatures, and ultraviolet or electron beam curable type resins are preferred. By using these, the polyester film can be processed at low temperatures during coating. Therefore, there is less thermal damage to the polyester film during processing, a polyester film with high flatness can be obtained, and defects such as pinholes can be reduced when manufacturing thin film resin sheets.

[0033] Examples of silicone resins used in addition reactions include those obtained by reacting polydimethylsiloxane, which has vinyl groups introduced to its terminals or side chains, with hydrodienesiloxane using a platinum catalyst and curing the reaction. In this case, it is preferable to use a resin that can be cured at 120°C in 30 seconds or less, as this allows for processing at lower temperatures. Examples include low-temperature addition-curing types (LTC1006L, LTC1056L, LTC300B, LTC303E, LTC310, LTC314, LTC350G, LTC450A, LTC371G, LTC750A, LTC755, LTC760A, etc.) and thermal UV-curing types (LTC851, BY24-510, BY24-561, BY24-562, etc.) from Dow Toray, as well as solvent addition + UV-curing types (X62-5040, X62-5065, X62-5072T, KS5508, etc.) and dual-cure curing types (X62-2835, X62-2834, X62-1980, etc.) from Shin-Etsu Chemical Co., Ltd.

[0034] Examples of silicone resins used in condensation reactions include those in which polydimethylsiloxane with OH groups at the ends and polydimethylsiloxane with H groups at the ends are condensed using an organotin catalyst to create a three-dimensional crosslinked structure.

[0035] Examples of UV-curable silicone resins include, as the most basic type, those that utilize the same radical reaction as conventional silicone rubber crosslinking, those that introduce unsaturated groups for photocuring, those that decompose onium salts with UV light to generate strong acids which then cleave epoxy groups and cause crosslinking, and those that crosslink through the addition reaction of thiols to vinylsiloxane. In addition, electron beams can be used instead of UV light. Electron beams have more energy than UV light, and it is possible to carry out a radical crosslinking reaction without using an initiator as in the case of UV curing. Examples of resins used include UV-curing silicones from Shin-Etsu Chemical Co., Ltd. (X62-7028A / B, X62-7052, X62-7205, X62-7622, ​​X62-7629, X62-7660, etc.), UV-curing silicones from Momentive Performance Materials Inc. (TPR6502, TPR6501, TPR6500, UV9300, UV9315, XS56-A2982, UV9430, etc.), and UV-curing silicones from Arakawa Chemical Corporation (Silicolise UV POLY200, POLY215, POLY201, KF-UV265AM, etc.).

[0036] As the UV-curing silicone resins mentioned above, acrylate-modified or glycidoxy-modified polydimethylsiloxanes can also be used. Good mold release properties can also be obtained by mixing these modified polydimethylsiloxanes with polyfunctional acrylate resins or epoxy resins and using them in the presence of an initiator.

[0037] Other suitable resins include alkyd resins and acrylic resins that have been modified by stearyl or lauryl, or alkyd resins, acrylic resins, and olefin resins obtained by the reaction of methylated melamine.

[0038] Examples of aminoalkyd resins obtained by the above-mentioned reaction of methylated melamine include Tesfine 303, Tesfine 305, and Tesfine 314, manufactured by Hitachi Chemical Co., Ltd. Examples of aminoacrylic resins obtained by the above-mentioned reaction of methylated melamine include Tesfine 322, manufactured by Hitachi Chemical Co., Ltd.

[0039] When using the above-mentioned resin in the release layer of the present invention, one type may be used, or two or more types may be mixed and used. In addition, it is possible to mix in additives such as light release additives and heavy release additives to adjust the release force.

[0040] The release layer of the present invention may contain additives such as adhesion enhancers and antistatic agents. Furthermore, to improve adhesion to the substrate, it is preferable to pre-treat the polyester film surface before applying the release layer, such as by applying an anchor coat, corona treatment, plasma treatment, or atmospheric pressure plasma treatment.

[0041] In the present invention, the thickness of the release layer can be set according to its intended use and is not particularly limited, but preferably, the thickness of the release layer after curing is in the range of 0.005 to 2.0 μm. A release layer thickness of 0.005 μm or more is preferable because it maintains peeling performance. Furthermore, a release layer thickness of 2.0 μm or less is preferable because the curing time does not become too long, and there is no risk of uneven thickness in the resin sheet due to a decrease in the flatness of the release film. In addition, because the curing time does not become too long, there is no risk of the resin constituting the release coating layer agglomerating and no risk of forming protrusions, so it is preferable that pinhole defects in the resin sheet do not occur easily.

[0042] The surface free energy of the release layer provided on the base film of the present invention is 12 mJ / m 2 Preferably, it is 18 mJ / m³. More preferably, 18 mJ / m³. 2 That is all. 20 mJ / m 2 The above is even more preferable. 12 mJ / m 2 This is preferable because it makes it less likely for the resin sheet dissolving solution to repel or otherwise occur when applied.

[0043] The surface free energy of the release layer provided on the base film of the present invention is 40 mJ / m 2 or less, which is preferable. More preferably, it is 35 mJ / m 2 or less, and 30 mJ / m 2 or less is even more preferable. A value of 40 mJ / m 2 or less is preferable because it provides good releasability of the molded resin sheet. In the present invention, the above surface free energy refers to at least the surface free energy of the surface of the release layer that is in contact with the resin sheet.

[0044] The water adhesion energy of the surface of the release layer of the present invention that is in contact with the resin sheet is, for example, 3.0 mJ / m 2 or more, and 3.5 mJ / m 2 or more is preferable. More preferably, it is 4.0 mJ / m 2 or more, and 5.5 mJ / m 2 or more is even more preferable. A value of 3.0 mJ / m 2 or more is preferable because it suppresses bulging at the coated edge when the solution for the resin sheet is applied. When bulging at the coated edge during coating is suppressed, edge waving is suppressed when the laminated film is wound into a roll, resulting in a good wound appearance, which is preferable because it provides good flatness of the laminated film.

[0045] Increasing the water adhesion energy on the surface of the release layer can be achieved by adding an additive to the release layer or adjusting the polymer composition. For example, in the case of a silicone resin, the water adhesion energy can be increased by introducing siloxane units having phenyl groups in side chains into the polydimethylsiloxane skeleton, or by adding T-unit (trifunctional) or Q-unit (tetrafunctional) silicone resin, or the like.

[0046] In addition to the methods described above, the water adhesion energy on the release layer surface can also be improved by changing the composition of the silicone resin. For example, the silicone resin in the addition reaction system can be cured by heating polydimethylsiloxane and hydrodienesiloxane, which have vinyl groups introduced at their ends or side chains, under a platinum catalyst. The water adhesion energy can also be changed by changing the molar amount of Si-H groups of the hydrodienesiloxane relative to the molar amount of terminal vinyl groups (Si-Vy). For example, a higher ratio of Si-H to Si-Vy tends to result in higher water adhesion energy, and a Si-H / Si-Vi ratio of 1.0 or higher is preferred, 1.5 or higher is more preferred, and 2.0 or higher is even more preferred.

[0047] In the present invention, the release layer is preferably made of the polyester substrate described above, and the arithmetic mean height (Sa) of the release layer is preferably 20 nm or less. Furthermore, it is particularly preferable that the arithmetic mean height (Sa) is 10 nm or less. When Sa is 20 nm or less, it is preferable because the occurrence of pinholes and localized thickness variations is less likely to occur during the molding of the resin sheet. It can be said that the smaller the arithmetic mean height (Sa) of the release layer, the better, but it may be 0.1 nm or more. Furthermore, the maximum protrusion height (P) of the release layer is preferably 500 nm or less, more preferably 200 nm or less, more preferably 150 nm or less, even more preferably 100 nm or less, for example, 85 nm or less, and particularly preferably 50 nm or less. If the maximum protrusion height (P) is 500 nm or less, defects such as pinholes and localized thinning do not occur during resin sheet formation, resulting in a good yield, which is preferable.

[0048] In the present invention, the method for forming the release layer is not particularly limited, and a method is used in which a coating solution containing a dissolved or dispersed release resin is applied to one side of a polyester film substrate, the solvent is removed by drying, and then the surface is heated, heat-cured, or ultraviolet-cured.

[0049] Any known coating method can be applied to the above-mentioned release layer. For example, conventional methods such as roll coating methods including gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0050] When a thermosetting material is used for the release layer, the drying temperature during solvent drying and heat curing is preferably 180°C or lower, more preferably 160°C or lower, even more preferably 140°C or lower, and most preferably 120°C or lower. The heating time is preferably 30 seconds or less, more preferably 20 seconds or less, and most preferably 10 seconds or less. When the temperature is 180°C or lower, the flatness of the film is maintained, and the risk of causing unevenness in the thickness of the resin sheet is small, which is preferable. When the temperature is 120°C or lower, processing can be done without impairing the flatness of the film, and the risk of causing unevenness in the thickness of the resin sheet is further reduced, which is particularly preferable. The lower limit of the drying temperature is not particularly limited, but it is preferably 60°C or higher. This is preferable because a release film can be obtained without any solvent remaining in the release layer at 60°C or higher.

[0051] When using an ultraviolet-curable material for the release layer, the drying temperature during solvent drying and heat curing is preferably 120°C or lower, more preferably 100°C or lower, and most preferably 90°C or lower. The heating time is preferably 30 seconds or less, more preferably 20 seconds or less, and most preferably 10 seconds or less. When the temperature is 120°C or lower, the flatness of the film is maintained, and the risk of causing unevenness in the thickness of the resin sheet is small, which is preferable. When the temperature is 90°C or lower, processing can be done without impairing the flatness of the film, and the risk of causing unevenness in the thickness of the resin sheet is further reduced, which is particularly preferable. The lower limit of the drying temperature is not particularly limited, but it is preferably 60°C or higher. This is preferable because a release film can be obtained without any solvent remaining in the release layer at 60°C or higher.

[0052] When using an ultraviolet-curable material for the release layer, it is preferable to irradiate it with active energy rays after solvent drying as described above to induce a curing reaction. Known technologies such as ultraviolet light and electron beams can be used as the active energy rays, but ultraviolet light is preferred. The integrated light quantity when using ultraviolet light can be expressed as the product of illuminance and irradiation time. For example, 10 to 500 mJ / cm². 2 It is preferable that the value is above the lower limit because it allows the release layer to harden sufficiently. It is also preferable that the value is below the upper limit because it suppresses thermal damage to the film due to heat during irradiation and maintains the smoothness of the release layer surface.

[0053] (Resin sheet) The laminated film of the present invention has a resin sheet disposed on the side of the release layer opposite to the substrate. For example, the resin sheet laminated onto the release film of the present invention is obtained by curing a resin sheet forming composition that contains at least a resin component (A) and a crosslinking agent (B). As a result of diligent research, the resin sheet of the present invention, when prepared under specific conditions described later, for example from the resin sheet forming composition according to the present invention, allows the resin component (A) and the crosslinking agent (B) to harden in a phase-separated state, forming appropriate irregularities on the surface of the resin sheet and enabling the resin sheet to exhibit slipperiness without containing particles or other inconsistencies.

[0054] The combined mass ratio of resin component (A) and crosslinking agent (B) preferably accounts for 80% or more by mass of the total solid content of the resin sheet, more preferably 90% or more by mass, and even more preferably 95% or more by mass. A content of 80% or more by mass is preferable because it improves the physical properties of the resin sheet, such as strength and heat resistance.

[0055] The preferred mass ratio of resin component (A) to crosslinking agent (B) is (A) / (B) = 90 / 10 to 50 / 50. A blending ratio of 10% by mass or more of crosslinking agent (B) is preferable because it increases the surface irregularities after phase separation, improving slipperiness. A blending ratio of 50% by mass or less of crosslinking agent (B) is preferable because it does not reduce the film strength of the resin sheet, provides excellent handling properties as a sheet, and prevents unreacted crosslinking agent from blocking the back surface of the laminated film when wound up. For example, it is preferable that the proportion of crosslinking agent (B) in the resin sheet to the total resin sheet is 10% by mass or more and 50% by mass or less. In one embodiment, the proportion of crosslinking agent (B) in the resin sheet to the total resin sheet is 10% by mass or more and less than 50% by mass, for example, 15% by mass or more and 45% by mass or less. By including crosslinking agent (B) under such conditions, the above effects can be achieved more effectively.

[0056] The resin component (A) is not particularly limited, and known resins can be used. For example, epoxy resins, phenoxy resins, polyester resins, urethane resins, fluororesins, acrylic resins, olefin resins, imide resins, sulfone resins, etc., can be used individually or mixed with two or more other types. The weight-average molecular weight (Mw) of the resin component (A) used in the present invention is 10,000 or more, preferably 10,000 to 200,000, and more preferably 30,000 to 100,000. A value of 10,000 or more is preferable because it results in a strong resin sheet with good handling properties. A value of 200,000 or less is preferable because it results in a lower viscosity of the solution when forming a film in solution, leading to better productivity. The method for measuring the weight-average molecular weight (Mw) is not particularly limited, but it can be measured using GPC or the like.

[0057] The crosslinking agent (B) is not particularly limited, and known crosslinking agents can be used. For example, isocyanates, melamine, carbodiimide, oxazoline, and other crosslinking agents can be used, and one type may be used or two or more types may be mixed. It is preferable that the crosslinking agent (B) reacts with the functional groups contained in the resin component (A). It is preferable that the crosslinking agent (B) contained in the resin sheet forming composition is liquid at 30°C. In this invention, liquid means that it has fluidity, for example, a viscosity of 10,000 mPa·s or less is sufficient. Being liquid at 30°C is preferable because it can effectively promote phase separation with the resin component (A) when drying the solution film of the resin sheet, making it easier to create surface irregularities in the resin sheet.

[0058] The resin sheet may contain additives other than the resin component (A) and crosslinking agent (B), as long as the above range is met. However, the resin sheet is substantially free of particles. The resin sheet according to the present invention is preferable because, due to its substantially particle-free nature, it is easier to obtain effects such as increased transparency of the molded resin sheet in optical applications, and improved electrical properties in electronic components such as dielectric sheets used in film capacitors. For example, in optical applications, the resin sheet may have a haze of 2% or less. Alternatively, the haze may be 1% or less. In one embodiment, the haze of the resin sheet is 0.1% or more. Also, in the case of electronic components such as film capacitors, the resin sheet may have a dielectric breakdown voltage of 200 V / μm or more. Alternatively, the dielectric breakdown voltage may be 300 V / μm or more. In one embodiment, the dielectric breakdown voltage is 500 V / μm or less.

[0059] The resin sheet of the present invention can have good slipperiness because, even if it does not substantially contain particles, there are minute irregularities on the surface caused by the phase separation of the resin component (A) and the crosslinking agent (B). The static friction coefficient of the resin sheet peeled from the base film is preferably 1.5 or less, more preferably 1.0 or less, and even more preferably 0.8 or less. A static friction coefficient of 1.5 or less is preferable because it improves winding and running properties and makes handling easier when the resin sheet is used in optical or electronic component applications. The static friction coefficient of the resin sheet may be 0.1 or more. In one embodiment, in Figure 2, the static friction coefficient measured by overlapping the surface (1) of the resin sheet indicated by reference numeral 13, which is opposite to the release layer, with the surface (2) of the resin sheet indicated by reference numeral 14, is 1.5 or less. The static friction coefficient measured under the above conditions is more preferably 1.0 or less, and even more preferably 0.8 or less. The static friction coefficient may also be 0.1 or more. Thus, by having the static friction coefficient measured by overlapping both sides of the resin sheet fall within the above range, the resin sheet of the present invention can achieve both high smoothness and excellent winding and running performance.

[0060] The arithmetic mean roughness (Sa) of the surface (1) (the surface opposite to the surface in contact with the release layer) of the resin sheet of the laminated film of the present invention is 2 nm or more and 30 nm or less, more preferably 2 nm or more and 20 nm or less, and even more preferably 2.5 nm or more and 15 nm or less. A roughness of 2 nm or more is preferable as it improves the slipperiness of the resin sheet. A roughness of 30 nm or less is preferable because it reduces the concern that defects such as pinholes will occur even when the resin sheet is peeled from the laminated film and only the resin sheet is wound into a roll.

[0061] The maximum cross-sectional height (St) of the surface (1) (the surface opposite to the surface in contact with the release layer) of the resin sheet of the laminated film of the present invention is 80 nm or more and 1000 nm or less, more preferably 100 nm or more and 600 nm or less, and even more preferably 150 nm or more and 500 nm or less. A height of 80 nm or more is preferable because it improves the slipperiness of the resin sheet. A height of 1000 nm or less is preferable because it reduces the concern that defects such as pinholes will occur even when the resin sheet is peeled from the laminated film and only the resin sheet is wound into a roll. Note that the maximum cross-sectional height (St) is the sum of the absolute values ​​of the maximum projection height (P) and the maximum valley depth (V).

[0062] The maximum protrusion height (P) of the resin sheet surface (1) of the laminated film of the present invention (the surface opposite to the surface in contact with the release layer) is preferably 500 nm or less, more preferably 250 nm or less, even more preferably 200 nm or less, and may be 185 nm or less, for example 150 nm or less, and particularly preferably 135 nm or less. For example, it may be 100 nm or less. If the maximum protrusion height (P) is 500 nm or less, it is preferable that defects such as pinholes do not occur even when the resin sheet is peeled from the laminated film and only the resin sheet is wound into a roll. It is preferable that the maximum protrusion height P is as small as possible, but it may be 1 nm or more, 3 nm or more, or even 35 nm or more.

[0063] By setting the arithmetic mean roughness (Sa) and maximum cross-sectional height (St) of the resin sheet surface (1) of the laminated film of the present invention within the aforementioned range, good slipperiness can be obtained even on a highly smooth surface. In particular, it is preferable to control the maximum cross-sectional height (St) within the above range.

[0064] In one embodiment, the maximum valley depth (V) of the surface (1) of the resin sheet of the laminated film is preferably 45 nm or more and 350 nm or less, for example, 45 nm or more and 300 nm or less, and preferably 45 nm or more and 250 nm or less. Having the maximum valley depth (V) within this range makes it easier to control the maximum cross-sectional height (St) within the aforementioned range even if the maximum protrusion height (P) is in the range of 250 nm or less, and thus improves the slipperiness of the resin sheet, which is preferable.

[0065] The arithmetic mean roughness (Sa) of the surface (2) (the surface in contact with the release layer) of the resin sheet of the laminated film of the present invention is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 5 nm or less. A roughness of 10 nm or less is preferable because it reduces the concern that defects such as pinholes will occur even when the resin sheet is peeled off from the laminated film and only the resin sheet is wound into a roll.

[0066] The film thickness (t1) of the resin sheet of the present invention is 1 μm or more and 20 μm or less. More preferably, it is 1 μm or more and 10 μm or less, and even more preferably, 2 μm or more and 8 μm or less. A film thickness (t1) of 1 μm or more of the resin sheet is preferable because it is less likely to tear after being peeled from the base film and can be easily handled. A film thickness (t1) of 20 μm or less of the resin sheet is preferable because the wet coating film thickness does not become too thick during solution film formation, making molding easier.

[0067] The indentation modulus (E1) of surface (1) and the indentation modulus (E2) of surface (2) of the resin sheet of the present invention are both 2.0 MPa or higher. More preferably, at least one of the indentation modulus (E1) of surface (1) and the indentation modulus (E2) of surface (2) is 2.2 MPa or higher, for example, 2.4 MPa or higher. An indentation modulus of 2.0 MPa or higher is preferable because it increases the film strength of the resin sheet and makes it easier to handle even after peeling it off the laminated film. There is no specific upper limit, but 20 MPa or less is preferable. For example, it may be 10 MPa or less, or 6 MPa or less. 20 MPa or less is preferable because it prevents the resin sheet from becoming too brittle and ensures good handling.

[0068] In the resin sheet of the present invention, the absolute value of the difference between the indentation modulus (E1) and the indentation modulus (E2) |E1-E2| is 1.5 or less, for example, less than 1.5 and preferably 1.3 MPa or less. More preferably 1.0 MPa or less, and more preferably 0.5 MPa or less. A difference of 1.3 MPa or less in the indentation modulus is preferable because it allows for the provision of a uniform resin sheet with no difference in physical properties in the thickness direction of the resin sheet. To achieve the above range, it is preferable to suppress segregation of the resin component (A) and crosslinking agent (B) within the resin sheet, which can be controlled by the conditions during coating and drying. For example, the absolute value |E1-E2|, which is the difference between the indentation modulus (E1) and the indentation modulus (E2), is preferably small and may be 0. In one embodiment, the absolute value |E1-E2| is 0.01 or greater, and may be 0.05 or greater. When the absolute value |E1-E2| is as described above, the processability of the resin sheet, such as its slipperiness, windability, and transportability, is excellent.

[0069] The film thickness (t1) of the resin sheet can be measured by known methods without particular limitations. For example, it can be measured by a contact-type film thickness gauge, an optical interferometry film thickness gauge, or by observing the cross-section with a scanning electron microscope or a transmission electron microscope.

[0070] As a method for laminating the resin sheet of the present invention onto a base film, it is preferable to form a coating solution containing at least the above-mentioned resin component (A) and crosslinking agent (B), dissolved or dispersed in an organic solvent or water, onto the release layer using a solution film forming method. Similar to the method for applying the release layer, it can be applied by known methods. For example, conventionally known methods such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0071] It is preferable that the process includes a heating step to dry and cure the solvent after applying the coating liquid to the release layer. The heating method is not particularly limited, but the laminated film after coating can be heated using hot air or infrared rays. The laminated film of the present invention is preferably coated and dried by roll-to-roll, and it is particularly preferable that the drying oven is a floating type or a roll-support type and uses hot air for drying.

[0072] The drying temperature is preferably such that the maximum temperature of the drying oven is 60°C to 160°C, more preferably 70°C to 140°C, and even more preferably 70°C to 130°C. A temperature of 60°C or higher is preferable because it reduces the amount of residual solvent in the resin sheet after drying, and there is no risk of deterioration in the performance of the resin sheet (for example, electrical properties in the case of dielectric layer applications). A temperature of 160°C or lower is preferable because there is no concern that wrinkles will form in the laminated film due to heat. Furthermore, if the temperature is higher than 160°C, there is a concern that the phase separation of the resin component and crosslinking agent in the resin sheet will progress too much, reducing the crosslinking density of the resin sheet, so it is preferable to keep the temperature at 160°C or lower. In one embodiment, the resin sheet of the present invention is a resin sheet heated under conditions of 70°C to 130°C.

[0073] The time between applying the coating liquid to the base film and placing it in the drying oven is preferably 5 seconds or less, more preferably 3 seconds or less, and even more preferably 2 seconds or less. A time of 5 seconds or less is preferable because it prevents excessive phase separation between the resin component and the crosslinking agent in the coating liquid, thus avoiding concerns about a decrease in the crosslinking density of the resin sheet.

[0074] After applying the coating liquid to the base film, the heating time in the drying oven at the maximum temperature is preferably 1 second or more, and preferably 2 seconds or more. A heating time of 1 second or more is preferable because it allows the reaction of the crosslinking agent to proceed. The upper limit of the heating time is 60 seconds or less, for example, preferably less than 60 seconds, more preferably 40 seconds or less, and even more preferably 20 seconds or less. A heating time of 60 seconds or less is preferable because it can suppress the extreme segregation of the crosslinking agent on the surface of the resin sheet and does not degrade the performance of the resin sheet.

[0075] By subjecting the resin sheet of the present invention to the above-described drying conditions, the phase separation of the resin component (A) and the crosslinking agent (B) is appropriately promoted, allowing the arithmetic mean roughness (Sa) and maximum cross-sectional height (St) of the resin sheet surface (1) to be controlled within the aforementioned range, and enabling the resin sheet to exhibit good slipperiness without the addition of particles.

[0076] (Laminated film) The laminated film of the present invention is used after the resin sheet is peeled off from the base film in subsequent processes. Therefore, a peel force of 800 mN / 25 mm width or less from the base film is preferable because it allows the resin sheet to be peeled off without tearing. More preferably, it is 500 mN / 25 mm width or less, even more preferably 300 mN / 25 mm width or less, and even more preferably 200 mN / 25 mm width or less. The peel force varies depending on the resin sheet being laminated, and can be adjusted by the type of release layer of the base film. [Examples]

[0077] Next, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the following examples. Furthermore, the evaluation methods used in the present invention are as follows.

[0078] (Arithmetic mean height (Sa), maximum protrusion height (P), maximum valley depth (V), maximum cross-sectional height (St)) The values ​​were measured using a non-contact surface shape measurement system (VertScan R550H-M100, manufactured by Ryoka Systems Co., Ltd.) under the following conditions. The arithmetic mean height (Sa) was the average of 5 measurements, while the maximum protrusion height (P) and maximum valley depth (V) were measured 7 times, and the maximum values ​​of the 5 measurements (excluding the maximum and minimum values) were used. The maximum cross-sectional height (St) was the sum of the absolute values ​​of the maximum protrusion height (P) and the maximum valley depth (V). (Measurement conditions) • Measurement mode: WAVE mode • Objective lens: 10x 0.5x Tube Lens ·Measurement area 936μm×702μm (Analysis conditions) • Surface correction: 4th order correction • Interpolation process: Full interpolation • Filtering: Gaussian cutoff value 50 μm

[0079] (Surface free energy) Under conditions of 25°C and 50% RH, droplets of water (1.8 μL) and diiodomethane (0.9 μL) were prepared on the release surface of a release film using a contact angle meter (Kyowa Interface Science Co., Ltd.: Fully Automatic Contact Angle Meter DM-701), and their contact angles were measured. The contact angles were taken 10 seconds after each liquid was dropped onto the release film. The contact angle data for water and diiodomethane obtained by the above method were calculated using the "Owens and Wendt" theory to determine the dispersion component γd of the surface free energy of the release film, and the component γh based on hydrogen bonding and dipole-dipole interaction. The sum of these components was used as the surface free energy γs. This calculation was performed using the analysis software within the contact angle meter software (FAMAS).

[0080] (Water adhesion energy) Under conditions of 25°C and 50% RH, a contact angle meter (Kyowa Interface Science Co., Ltd.: Fully Automatic Contact Angle Meter DM-701) was used to drop water (droplet volume 10 μL) onto the release surface of a release film. Two seconds after dropping, the stage was continuously tilted, and the contact angle was measured at 1° intervals. The tilt angle when the droplet moved 5 dots from the 0° position was determined as the sliding angle, and the adhesion energy was calculated from this. This calculation was performed using the analysis software within the contact angle meter software (FAMAS).

[0081] (film thickness) The cut laminated films were embedded in resin and then ultrathin sectioned using an ultramicrotome. Subsequently, they were observed at a direct magnification of 20,000x using a JEOL JEM2100 transmission electron microscope, and the film thickness of each layer of the laminated film was measured from the observed TEM images.

[0082] (Peeling force) The laminated film was cut into strips 25 mm wide and 150 mm long. One end of the base film was fixed, and one end of the resin sheet was supported. The resin sheet side was then pulled at a speed of 300 mm / min, and the T-shaped peel strength was measured. A tensile testing machine ("AUTOGRAPH AG-X" manufactured by Shimadzu Corporation) was used for the measurement. The average value of five measurements was adopted. The peelability was evaluated based on the measured peeling force according to the following criteria. ○: It was possible to peel it off with a low peeling force of 100mN / 25mm width or less, and even thin films could be peeled off without tearing. ○△: Peeling was possible with a peeling force of 300mN / 25mm width or less and greater than 100mN / 25mm width. △: Peeling force was greater than 300mN / 25mm width, and peeling was possible with 800mN / 25mm width or less. In areas with extremely thin film thickness, some tearing occurred. ×: It could not be removed.

[0083] (Static friction coefficient and slipperiness evaluation) The static friction coefficient of the resin sheet was measured as follows, and its slipperiness was evaluated. The resin sheet was peeled from the laminated film and fixed to the bottom surface of a 1.4 kg metal rectangular prism with surface (2) facing outwards. Next, the resin sheet was fixed to a flat metal plate with adhesive tape so that surface (1) facing outwards. The metal rectangular prism was placed so that surface (1) and surface (2) were in contact, and the static friction coefficient was measured at a tensile speed of 200 mm / min under 23°C and 65% RH conditions. The slipperiness was judged according to the following criteria. ○ : 0.1 < μs ≤ 0.8 △ : 0.8 < μs ≤ 1.5 ×: Values ​​exceeding 1.5 or the coefficient of friction is too high to measure.

[0084] (Electrical characteristics) A thin aluminum vapor-deposited layer was applied to both sides of a resin sheet peeled from a base film, and the dielectric breakdown voltage (V / μm) was measured at room temperature. The average value of 10 measurements was used for evaluation according to the following criteria. ○: Dielectric breakdown voltage (BDV value) of 300V / μm or higher △: Dielectric breakdown voltage is 200V / μm or higher ×: Dielectric breakdown voltage is less than 200V / μm

[0085] (Indentation modulus) The indentation modulus of the resin sheet was measured as follows. The resin sheet was peeled from the laminated film and fixed to a stainless steel sample stage using double-sided adhesive tape with the measurement surface facing upwards. The measurement sample was then subjected to a scanning probe microscope (Shimadzu Corporation, "SPM-9700") under the following conditions, and the force curve was measured. Based on the obtained force curve shape, the elastic modulus was calculated using the JKR two-point method with the software included in the instrument. Cantilever: Team Nanotec silicone probe "LRCH" (Spring constant: 0.3 N / m, radius of curvature: 250 nm, cantilever half-vertex angle: 45 deg, Poisson's ratio: 0.50 were set.) Sensitivity: 150 nm / V (The sensitivity was determined using a value based on a stainless steel plate before measurement.) Sweep speed: 1Hz (2000nm / s) *The indentation depth from the sample surface was approximately 20 nm.

[0086] (Preparation of polyethylene terephthalate pellets (PET(I))) A continuous esterification reactor consisting of a three-stage complete mixing tank equipped with a stirrer, a partial condenser, a raw material inlet, and a product outlet was used as the esterification reactor. Terephthalic acid (TPA) was supplied at a rate of 2 tons / hour, ethylene glycol (EG) at a ratio of 2 moles per mole of TPA, and antimony trioxide was added in an amount that resulted in 160 ppm of Sb atoms relative to the produced PET. This slurry was continuously supplied to the first esterification reactor of the esterification reactor and reacted at atmospheric pressure at 255°C for an average residence time of 4 hours. Next, the reaction products from the first esterification reactor were continuously removed from the system and supplied to the second esterification reactor. EG distilled off from the first esterification reactor was supplied to the second esterification reactor at 8% by mass relative to the generated PET. Furthermore, an EG solution containing magnesium acetate tetrahydrate in an amount that resulted in 65 ppm of Mg atoms relative to the generated PET, and an EG solution containing TMPA (trimethyl phosphate) in an amount that resulted in 40 ppm of P atoms relative to the generated PET were added, and the reaction was carried out at atmospheric pressure at 260°C for an average residence time of 1 hour. Next, the reaction products from the second esterification reactor were continuously removed from the system and supplied to the third esterification reactor, and the mixture was dispersed at 39 MPa (400 kg / cm²) using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.). 2 0.2% by mass of porous colloidal silica with an average particle size of 0.9 μm, which was dispersed by a dispersion treatment with an average of 5 passes at a pressure of ) and 0.4% by mass of synthetic calcium carbonate with an average particle size of 0.6 μm, which had 1% by mass of polyacrylic acid ammonium salt attached to calcium carbonate, were added as 10% EG slurry each and reacted at atmospheric pressure at 260°C with an average residence time of 0.5 hours. The esterification reaction product generated in the third esterification reaction vessel was continuously supplied to a three-stage continuous polycondensation reaction apparatus to perform polycondensation, and after filtration with a filter made of sintered stainless steel fibers with a 95% cut diameter of 20 μm, it was extruded into water by ultrafiltration, cooled and cut into chips to obtain PET chips with an intrinsic viscosity of 0.60 dl / g (hereinafter abbreviated as PET(I)). The lubricant content in the PET chips was 0.6% by mass.

[0087] (Preparation of polyethylene terephthalate pellets (PET(II))) On the other hand, in the production of the above-mentioned PET chip, a PET chip with an intrinsic viscosity of 0.62 dl / g that does not contain any particles such as calcium carbonate or silica was obtained (hereinafter abbreviated as PET(II)).

[0088] (Preparation of polyethylene terephthalate pellets (PET(III))) Except for changing the particle type and content of PET(I) to 0.75% by mass of synthetic calcium carbonate with an average particle size of 0.9 μm, which is formed by attaching 1% by mass of polyacrylic acid ammonium salt to calcium carbonate, a PET chip was obtained in the same manner as PET(I) (hereafter referred to as PET(III)). (Abbreviated as ). The lubricant content in the PET chip was 0.75% by mass.

[0089] (Manufacturing of base film X1) After drying, these PET chips were melted at 285°C and then melted again at 290°C in a separate extruder. A two-stage filtration process was performed using a filter made of sintered stainless steel fibers with a 95% cut diameter of 15 μm and a filter made of sintered stainless steel particles with a 95% cut diameter of 15 μm. The mixture was then combined in a feed block, laminating PET(I) as surface layer B and PET(II) as surface layer A. The resulting sheet was extruded (cast) at a speed of 45 m / min and electrostatically adhered and cooled on a casting drum at 30°C using the electrostatic adhesion method to obtain an unstretched polyethylene terephthalate sheet with an intrinsic viscosity of 0.59 dl / g. The layer ratio was adjusted so that PET(I) / PET(II) = 60% / 40% based on the discharge rate calculations of each extruder. Next, this unstretched sheet was heated with an infrared heater and then stretched 3.5 times in the longitudinal direction by the speed difference between the rolls at a roll temperature of 80°C. Subsequently, the material was guided into a tenter and stretched 4.2 times laterally at 140°C. Next, it was heat-treated at 210°C in a heat-fixing zone. After that, a 2.3% relaxation treatment was performed laterally at 170°C to obtain a biaxially oriented polyethylene terephthalate base film X1 with a thickness of 25 μm. The Sa of surface layer A of the obtained base film X1 was 2 nm, and the Sa of surface layer B was 29 nm.

[0090] (Manufacturing of a base film X2 having a release layer) On the surface layer A of the base film X1 obtained above, the release coating liquid Y1 described below was applied by reverse gravure coating to a wet film thickness of 5 μm, and then dried and cured in a hot air drying oven at 120°C for 30 seconds to obtain a base film X2 with a release layer. The Sa of the surface of the release layer was 2 nm. (Release coating solution Y1) Toluene 48 parts by mass Methyl ethyl ketone 48 parts by mass Silicone resin composition (1) (Thermosetting silicone coating material, Si-H / Si-Vy=3.0, solids content 30% by mass) 3 parts by mass SRX212P Catalyst (Pt-based curing catalyst manufactured by Dow Toray) 0.1 part by mass

[0091] (Manufacturing of base film X3 having a release layer) Without changing the layer structure and stretching conditions, similar to that of base film X1, the thickness was adjusted by changing the casting speed to create a biaxially oriented polyethylene terephthalate film with a thickness of 12 μm. A release layer similar to that of X2 was then added to obtain base film X3. The Sa of surface layer A of the obtained film X3 was 3 nm, and the Sa of surface layer B was 29 nm.

[0092] (Method for manufacturing a base film X4 having a release layer) For the base film X4, a 25 μm thick A4100 (Cosmoshine®, manufactured by Toyobo Co., Ltd.) was used, with a release layer similar to that of X2 provided on surface layer A. A4100 has a structure in which the film substantially does not contain particles, and a coating layer containing particles is provided only on the surface layer B side by inline coating. The Sa of surface layer A of base film X4 was 1 nm, and the Sa of surface layer B was 2 nm.

[0093] (Method for manufacturing a base film X5 having a release layer) As the base film X5, a release layer similar to that of X2 was provided on surface layer A of E5101 (Toyobo Ester® film, manufactured by Toyobo Co., Ltd.), which has a thickness of 25 μm. E5101 has a structure in which particles are contained in surface layers A and B of the film. The Sa of surface layer A of base film X5 was 25 nm, and the Sa of surface layer B was 25 nm.

[0094] (Method for manufacturing a base film X6 having a release layer) The following release coating liquid Y2 was applied to the surface layer A of the base film X1 by reverse gravure coating to a wet film thickness of 5 μm, and then dried and cured in a hot air drying oven at 120°C for 30 seconds to obtain a base film X6 with a release layer. The Sa of the surface of the release layer was 2 nm. (Release coating solution Y2) Toluene 48 parts by mass Methyl ethyl ketone 48 parts by mass Silicone resin composition (2) (Thermosetting silicone coating material, Si-H / Si-Vy=1.0, solids content 30% by mass) 3 parts by mass SRX212P Catalyst (Pt-based curing catalyst manufactured by Dow Toray) 0.1 part by mass

[0095] (Method for manufacturing a base film X7 having a release layer) The following release coating solution Y3 was applied to the surface layer A of the base film X1 using a reverse gravure coating method to a wet film thickness of 5 μm, and then dried and cured in a hot air drying oven at 120°C for 30 seconds to obtain a base film X7 with a release layer. The Sa of the surface of the release layer was 2 nm. (Release coating solution Y3) Toluene 48 parts by mass Methyl ethyl ketone 48 parts by mass Silicone resin composition (3) (Thermosetting silicone coating material, Si-H / Si-Vy=2.2, solids content 30% by mass) 3 parts by mass SRX212P Catalyst (Pt-based curing catalyst manufactured by Dow Toray) 0.1 part by mass

[0096] (Example 1) A resin solution Z is applied to the surface layer A of the base film X2 using the reverse gravure coating method. The resin sheet was coated with material 1 so that the film thickness after drying was 3 μm, and then dried in a hot air drying oven at 120°C for 10 seconds to form the resin sheet and create a laminated film. (At this time, 2 seconds elapsed between coating and entering the drying oven). Details are shown in Tables 1 and 2. (Resin solution Z1) Methyl ethyl ketone 41.3 parts by mass Tetrahydrofuran 22.5 parts by mass PKHB solution (solid content 40% by mass) 30.6 parts by mass (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000) *The solution was prepared by dissolving phenoxy resin in tetrahydrofuran. Millionate MR-200 5.3 parts by mass (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 200 mPa·s, solids content 99% by mass) BYK-370 0.4 parts by mass (Manufactured by Big Chemie Japan, a silicone-based surfactant)

[0097] (Examples 2-3) A laminated film was prepared in the same manner as in Example 1, except that the base film was changed to one of those listed in Table 1.

[0098] (Example 4) A laminated film was prepared in the same manner as in Example 1, except that the resin component (A) was changed to a resin solution Z6 with a different weight-average molecular weight (Mw). (Resin solution Z6) Methyl ethyl ketone 41.3 parts by mass Tetrahydrofuran 22.5 parts by mass PKHJ solution (solid content 40% by mass) 30.6 parts by mass (Phenoxy resin manufactured by Gabriel Phenoxies, Mw57000) *The solution was prepared by dissolving phenoxy resin in tetrahydrofuran. Millionate MR-200 5.3 parts by mass (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 200 mPa·s, solids content 99% by mass) BYK-370 0.4 parts by mass (Manufactured by Big Chemie Japan, a silicone-based surfactant)

[0099] (Example 5) A laminated film was prepared in the same manner as in Example 1, except that the resin solution Z2 was used to change the type of crosslinking agent. (Resin solution Z2) Methyl ethyl ketone 41.3 parts by mass Tetrahydrofuran 22.5 parts by mass PKHB solution (solid content 40% by mass) 30.6 parts by mass (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000) *The solution was prepared by dissolving phenoxy resin in tetrahydrofuran. Millionate MR-400 5.3 parts by mass (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 600 mPa·s, solids content 99% by mass) BYK-370 0.4 parts by mass (Manufactured by Big Chemie Japan, a silicone-based surfactant)

[0100] (Example 6) A laminated film was prepared in the same manner as in Example 1, except that the type of crosslinking agent was changed to resin solution Z3. (Resin solution Z3) Methyl ethyl ketone 41.3 parts by mass Tetrahydrofuran 22.5 parts by mass PKHB solution (solid content 40% by mass) 30.6 parts by mass (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000) *The solution was prepared by dissolving phenoxy resin in tetrahydrofuran. Millionate MTL 5.3 parts by mass (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 50 mPa·s, solids content 99% by mass) BYK-370 0.4 parts by mass (Manufactured by Big Chemie Japan, a silicone-based surfactant)

[0101] (Example 7) A laminated film was prepared in the same manner as in Example 1, except that the resin solution Z4 was used to change the ratio of resin to crosslinking agent. (Resin solution Z4) Methyl ethyl ketone 41.3 parts by mass 19.9 parts by mass of tetrahydrofuran PKHB solution (solid content 40% by mass) 35.0 parts by mass (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000) *The solution was prepared by dissolving phenoxy resin in tetrahydrofuran. Millionate MR-200 3.5 parts by mass (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 200 mPa·s, solids content 99% by mass) BYK-370 0.4 parts by mass (Manufactured by Big Chemie Japan, a silicone-based surfactant)

[0102] (Example 8) A laminated film was prepared in the same manner as in Example 1, except that the resin solution Z5 was used to change the ratio of resin to crosslinking agent. (Resin solution Z5) Methyl ethyl ketone 41.3 parts by mass 17.3 parts by mass of tetrahydrofuran PKHB solution (solid content 40% by mass) 39.4 parts by mass (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000) *The solution was prepared by dissolving phenoxy resin in tetrahydrofuran. Millionate MR-200 1.8 parts by mass (Manufactured by Tosoh Corporation, isocyanate crosslinking agent, viscosity 200 mPa·s, solids content 99% by mass) BYK-370 0.4 parts by mass (Manufactured by Big Chemie Japan, a silicone-based surfactant)

[0103] (Examples 9-11) A laminated film was prepared in the same manner as in Example 1, except that the base film was changed to the one shown in Table 1.

[0104] (Examples 12-13) A laminated film was prepared in the same manner as in Example 1, except that the drying temperature of the resin sheet was changed to the temperature listed in Table 1.

[0105] (Comparative Example 1) A laminated film was prepared in the same manner as in Example 1, except that the base film was changed to X1, which does not have a release layer.

[0106] (Comparative Example 2) A laminated film was prepared in the same manner as in Example 1, except that the resin solution was changed to resin solution Z6 which does not contain a crosslinking agent. (Resin solution Z6) Methyl ethyl ketone 41.3 parts by mass 14.7 parts by mass of tetrahydrofuran PKHB solution (solid content 40% by mass) 43.8 parts by mass (Phenoxy resin manufactured by Gabriel Phenoxies, Mw32000) *The solution was prepared by dissolving phenoxy resin in tetrahydrofuran. BYK-370 0.4 parts by mass (Manufactured by Big Chemie Japan, a silicone-based surfactant)

[0107] (Comparative Example 3) A laminated film was prepared in the same manner as in Example 1, except that the resin sheet was formed so that the maximum cross-sectional height (St) of the surface (1) of the resin sheet was 75 nm.

[0108] (Reference example 4) A laminated film was prepared in the same manner as in Example 1, except that the drying conditions for the resin sheet were changed to 140°C for 60 seconds. Increasing the drying time increased the precipitation of the crosslinking agent on the surface, resulting in a rougher surface condition and a significant difference in the indentation modulus between the front and back surfaces of the resin sheet.

[0109] The base film used in each example was processed with a release layer and then aged at 40°C for 3 days before use. The resulting laminated film was also evaluated after being aged at 40°C for 3 days.

[0110] [Table 1]

[0111] [Table 2]

[0112] The laminated sheet of the present invention obtained in the examples is a resin sheet that can enhance transparency and other properties in optical applications, for example, and moreover, can provide a resin sheet that exhibits high smoothness. Furthermore, it can achieve both high smoothness and high slipperiness, which can suppress scratches during processes such as transportation, and avoid a decrease in yield. Furthermore, for electronic component applications such as film capacitors, the resin sheet can provide high smoothness, improving electrical properties such as dielectric breakdown voltage. Moreover, it can achieve both high smoothness and high slipperiness, suppressing winding misalignment and wrinkles when winding the dielectric resin sheet onto a roll, resulting in excellent winding performance. Therefore, it is possible to transport the capacitor while maintaining its superior performance. Furthermore, the resin sheet obtained by this invention is substantially particle-free, avoiding insufficient transparency such as increased internal haze. It also avoids the problem of uneven particle distribution on the resin sheet, resulting in good slipperiness.

[0113] In contrast, Comparative Example 1 lacked the release layer according to the present invention, resulting in extremely poor peelability of the resin sheet, making it impossible to evaluate the resin sheet. Comparative Example 2, lacking a crosslinking agent in the resin sheet forming composition, showed particularly poor slipperiness of the resin sheet. Comparative Example 3 showed a particularly poor slipperiness of the resin sheet because the maximum cross-sectional height (St) of the surface (1) of the resin sheet was outside the range of the present invention. [Industrial applicability]

[0114] This invention relates to a laminated film made by laminating resin sheets, and more particularly to a laminated film made by laminating resin sheets used in electronic components and optical applications. [Explanation of symbols]

[0115] 10. Base film 11 Release layer 12 Resin Sheets 13 Surface of the resin sheet (1) 14 Surface of the resin sheet (2)

Claims

1. The film comprises a polyester-based base film, a release layer disposed on at least one side of the base film, and a resin sheet disposed on the side of the release layer opposite to the base film. Laminated film that meets the following criteria: The aforementioned resin sheet is obtained by curing a resin sheet forming composition that includes at least a resin component (A) and a crosslinking agent (B). The aforementioned resin sheet is substantially free of particles, The film thickness (t1) of the aforementioned resin sheet is 1 μm or more and 20 μm or less. The indentation modulus (E1) of the resin sheet surface (1) is 2.0 MPa or more. The indentation modulus (E2) of the resin sheet surface (2) is 2.0 MPa or more. The absolute value of the difference between E1 and E2 is 1.5 or less. The static friction coefficient measured by overlapping the surface (1) of the resin sheet opposite to the release layer surface and the surface (2) of the resin sheet on the release layer side is 1.5 or less. The aforementioned resin component (A) includes a phenoxy resin. The crosslinking agent (B) is an isocyanate, The surface free energy of the release layer surface is 40 mJ / m² or less, and the water adhesion energy is 3.5 mJ / m² or more. Laminated film.

2. The laminated film according to claim 1, characterized in that the arithmetic mean height (Sa) of the surface (1) of the resin sheet is 2 nm or more and 30 nm or less.

3. The laminated film according to claim 1, characterized in that the maximum cross-sectional height (St) of the surface (1) of the resin sheet is 80 nm or more and 1000 nm or less.

4. The laminated film according to claim 1, characterized in that the crosslinking agent (B) contained in the resin sheet forming composition is liquid at 30°C.

5. The laminated film according to claim 1, characterized in that the proportion of the crosslinking agent (B) contained in the resin sheet to the total resin sheet is 10% by mass or more.

6. The laminated film according to claim 1, characterized in that the weight-average molecular weight of the resin component (A) contained in the resin sheet is 10,000 or more.

7. The laminated film according to claim 1, wherein the maximum valley depth (V) of the surface (1) of the resin sheet of the laminated film is 45 nm or more and 350 nm or less.

8. The laminated film according to claim 1, characterized in that the arithmetic mean height (Sa) of the release layer side surface of the base film is 20 nm or less, and the maximum protrusion height (P) is 500 nm or less.

9. A method for manufacturing a laminated film according to any one of claims 1 to 8, characterized in that a resin sheet is coated and molded onto a base film by a solution film forming method.

10. Resin sheet that meets the following requirements: The aforementioned resin sheet is obtained by curing a resin sheet forming composition that includes at least a resin component (A) and a crosslinking agent (B). The aforementioned resin sheet is substantially free of particles, The film thickness (t1) of the aforementioned resin sheet is 1 μm or more and 20 μm or less. The indentation modulus (E1) of the resin sheet surface (1) is 2.0 MPa or more. The indentation modulus (E2) of the resin sheet surface (2) is 2.0 MPa or more. The absolute value of the difference between E1 and E2 is 1.5 or less. One surface (1) of the resin sheet and the front surface of the resin sheet The static friction coefficient measured by superimposing the surface (1) on the opposite surface (2) is 1.5 or less. The weight-average molecular weight of the resin component (A) contained in the aforementioned resin sheet is 10,000 or more. The aforementioned resin component (A) includes a phenoxy resin. The crosslinking agent (B) is an isocyanate. Resin sheet.

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